One of the troubles with having a large homeless population is that people aren't rooted in one place and easily lose contact with one another. People blame authorities for disappearances and are particularly suspicious of vehicles idling for long periods to no apparent purpose.
In Sacramento, 'Joe the Plumber' says the homeless are being swept into mobile crematoria (semi-trailers called 'Smokies') that patrol inner city neighborhoods in the day and incinerate people in the outskirts of the city at night.
Similarly, in Albuquerque, people accuse ambulance drivers of organ harvesting. (h/t John)